What happens when the hurricane chasers land on Ian?


(The Conversation) – As Hurricane Ian intensifies on its way to the Florida coast, hurricane chasers are in the skies doing something almost unimaginable: flying into the center of the storm. On each pass, scientists aboard these planes take measurements that satellites cannot and send them to forecasters at the National Hurricane Center.

Jason Dunion, a meteorologist at the University of Miami, leads the National Oceanic and Atmospheric Administration’s 2022 Hurricane Field Program. He described the technology the team uses to assess hurricane behavior in real time and the experience aboard a P-3 Orion as it dives through a hurricane’s eyewall.

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What happens aboard a hurricane chaser when you fly in a storm?

Basically, we take a flying lab into the heart of the hurricane, up to Category 5. As we fly, we process data and send it to forecasters and climate modellers.

In the P-3s, we regularly ride through the middle of the storm, right in the eyes. Imagine an X pattern – we keep going through the storm many times during a mission. These may be developing or Category 5 storms.

Inside the eye of Hurricane Teddy in 2020. The eye is the calmest part of the storm, but it’s surrounded by the most intense part: the eyewall. Lt Cmdr. Robert Mitchell/NOAA Corps

We typically fly at an altitude of around 10,000 feet, about a quarter of the way from the ocean surface to the top of the storm. We want to get through the roughest part of the storm because we’re trying to measure the strongest winds for the Hurricane Center.

It must be intense. Can you describe what the scientists experience on these flights?

My strongest flight was Dorian in 2019. The storm was near the Bahamas and was rapidly intensifying to a very strong Category 5 storm, with winds around 185 mph. It was like being a feather in the wind.

When we were going through Dorian’s eyewall, there were only seat belts. You can lose a few hundred feet in seconds if you have a downdraft, or you can hit an updraft and gain a few hundred feet in seconds. It’s kind of like a roller coaster ride, except you don’t know exactly when the next high or low is coming.

View of Earth and a large hurricane from a portal on the space station.
Hurricane Dorian seen from the International Space Station. NASA Expedition 60

At one point, we had G-forces of 3 to 4 G. That’s what astronauts experience during a rocket launch. We can also get zero G for a few seconds, and anything untethered will float.

Even in the toughest parts of the storm, scientists like me are busy with computers processing the data. A technician in the back may have launched a drop sounder from the belly of the plane, and we’re checking the quality of the data and sending it to the modeling centers and the National Hurricane Center.

The plane on a runway at sunrise.
NOAA’s P-3 Orion nicknamed ‘Kermit’ prepares to take off. Lt Cmdr Rannenberg / NOAA Corps

What do you learn about hurricanes from these flights?

One of our goals is to better understand why storms are rapidly intensifying.

Rapid intensification occurs when a storm increases its speed by 35 mph in a single day. This is equivalent to going from Category 1 to a major Category 3 storm in a short time. Ida (2021), Dorian (2019), and Michael (2018) are just a few recent hurricanes that have rapidly intensified. When this happens close to land, it can catch people off guard, and it quickly becomes dangerous.

Since a rapid intensification can occur in a very short period of time, we need to be out there with the hurricane hunters taking action as the storm builds up.

A pilot at the controls with the storm seen through the window
A hurricane chaser flies over Hurricane Ida in 2021. Lt. Cmdr. Kevin Doremus/NOAA Corps

So far, a rapid escalation is hard to predict. We might start to see the ingredients coming together quickly: Is the ocean warm at great depths? Is the atmosphere pleasant and juicy, with plenty of humidity around the storm? Are the winds favourable? We also look at the inner core: what does the structure of the storm look like and is it starting to consolidate?

Satellites can give forecasters a basic view, but we need to get our hurricane hunters into the storm itself to really make out the hurricane.

What does a storm look like when it intensifies rapidly?

Hurricanes like to stand up straight – think of a spinning top. So one thing we’re looking for is alignment.

A storm that is not yet fully formed may have a low level circulation a few kilometers above the ocean that is not aligned with its mid level circulation 6 or 7 kilometers above. It’s not a very healthy storm. But a few hours later, we might go back into the storm and notice that the two centers are more aligned. This is a sign that it could quickly escalate.

We also look at the boundary layer, the area just above the ocean. Hurricanes breathe: they draw in air at low levels, the air rises at the eyewall, and then it vents at the top of the storm and away from the center. That’s why we have these huge updrafts in the eyewall.

So we could look at our dropsonde or tail doppler radar data to find out how the winds are flowing at the boundary layer. Is it really moist air rushing towards the center of the storm? If the boundary layer is deep, the storm can also take a deeper breath.

What happens when the hurricane chasers land on Ian?
Cross section of a hurricane. National Weather Service

We also look at the structure. Often the storm looks healthy on the satellite, but we’ll come in with the radar and the structure is sloppy or the eye may be filled with cloud, telling us the storm isn’t quite ready to move in. rapidly intensify. But, during this flight, we might start to see the structure change quite rapidly.

Air flowing in, out, and out – breathing – is a great way to diagnose a storm. If this breathing feels healthy, it can be a good sign of an intensifying storm.

What instruments do you use to measure and predict the behavior of hurricanes?

We need instruments that measure not only the atmosphere but also the ocean. Winds can drive a storm or tear it apart, but the heat and humidity of the ocean are its fuel.

We use dropsondes to measure temperature, humidity, pressure and wind speed, and send data back every 15 feet or so down to the ocean surface. All of this data is passed to the National Hurricane Center and modeling centers so they can get a better representation of the atmosphere.

A scientist in a flight suit puts a device in a tube at the bottom of the plane to knock it down.
A NOAA technician deploys an airborne disposable bathythermograph. Paul Chang/NOAA

A P-3 is equipped with a laser – a CRL, or Compact Rotating Raman LiDAR – that can measure temperature, humidity and aerosols from the aircraft to the ocean surface. This can give us an idea of ​​the freshness of the atmosphere, therefore of its capacity to feed a storm. The CRL runs continuously throughout the entire flight path, so you get that beautiful curtain under the plane showing temperature and humidity.

The planes are also equipped with tail Doppler radars, which measure the way moisture droplets in the air blow to determine wind behavior. This gives us a 3D view of the wind field, like an x-ray of the storm. You can’t get that from a satellite.

We are also launching ocean probes called AXBT (non-recoverable aircraft bathythermograph) ahead of the storm. These probes measure the temperature of the water over several hundred meters. Generally, a surface temperature of 26.5 degrees Celsius (80 Fahrenheit) and above is favorable for a hurricane, but the depth of this heat is also important.

If you have warm ocean water that is maybe 85 F at the surface, but just 50 feet away the water is a bit colder, the hurricane is going to mix with that water pretty quickly. cold and weaken the storm. But deep warm water, like that found in eddies in the Gulf of Mexico, provides additional energy that can fuel a storm.

This year we are also testing new technologies – small drones that we can launch from the belly of a P-3. They have a wingspan of around seven to nine feet and are basically a weather station with wings.

One of these drones dropped into the eye could measure changes in pressure, which indicates if a storm is strengthening. If we could drop a drone into the eyewall and orbit it there, it could measure where the strongest winds are – that’s another important detail for forecasters. We also don’t have many measurements in the boundary layer because it’s not a safe place for an aircraft.

You also targeted the Cape Verde Islands off Africa for the first time this year. What are you looking for there?

The Cape Verde islands are in the Atlantic hurricane nursery. Hurricane seedlings are coming out of Africa, and we’re trying to figure out the tipping points for those disturbances to turn into storms.

More than half of the named storms we get in the Atlantic come from this nursery, including about 80% of major hurricanes, so that’s important, even though the disturbances are maybe 7-10 days ahead of the formation of a hurricane.

In Africa, many thunderstorms develop along the southern border of the Sahara Desert with the cooler and wetter Sahel region in summer. The difference in temperature can cause ripples to develop in the atmosphere which we call tropical waves. Some of these tropical waves are precursors to hurricanes. However, the Saharan air layer – huge dust storms that smash across Africa every three to five days or so – can suppress a hurricane. These thunderstorms peak from June to mid-August. After that, tropical disturbances are more likely to reach the Caribbean.

At some point not too far in the future, the National Hurricane Center will need to make a seven-day forecast, rather than just a five-day forecast. We are thinking about how to improve these first forecasts.


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